As announcements of carbon neutral goals from companies, communities, states and countries continue to grow, the power industry is preparing for an intense surge of renewable generation on the grid. New solar and wind generation infrastructure will need to be added to meet these looming neutrality dates. Unfortunately, modeling shows that increased renewable integration in the grid will also increase the need to curtail the power generated if effective storage is not also in place.

Though batteries offer an opportunity to store excess renewable energy, they are unlikely to be able to meet all needs for heightened capacity going forward. To fill the existing gaps and further optimize renewable energy, technology is being tested to convert generated power to methane and hydrogen gases.

The Power-to-Gas Solution

While natural gas-fired plants are today’s bridge to connect the intermittency of renewable generation with the reliability demands of consumers, conversion to methane or hydrogen might be the bridge of the future. Unlike natural gas, methane and hydrogen developed utilizing renewable fuels are net-zero or carbon neutral fuels.

The process to convert renewable-generated power to methane gas requires three steps:

  1. Carbon dioxide is captured from the atmosphere.
  2. Hydrogen is made through electrolysis of water.
  3. The carbon dioxide and hydrogen are combined through methanization to create methane.

In contrast, hydrogen is created simply through the single electrolysis step.

Once either methane or hydrogen is created, both can be stored for long-term backup power. If a wind farm has to shut down due to hurricane-force winds or if a weeklong cloudy spell hits a region, the converted renewable gas can sustain power supplies during those extended downtimes — far longer than current battery systems can.

The availability of flexible, renewable methane or hydrogen also opens up infrastructure possibilities for utilities. By maximizing the use of solar and wind power — through immediate use, short-term battery storage and long-term renewable gas storage — utilities can minimize the generation sites needed. Solar and wind farms occupy a great deal of real estate, which can be expensive to acquire and maintain. However, increasing the efficiency of the systems that use and store the power generated can reduce capital costs and help reach net-zero carbon goals faster than originally anticipated.

Considerations for a Low-Carbon Future

Renewable power to methane or hydrogen gas is still a fairly new approach, requiring several considerations by utilities. For example, power to methane is a more expensive approach because it requires more process equipment and technology to create the gas. However, costs can be recouped by using existing storage and transmission facilities and infrastructure. Methane can also be liquefied in the same manner that natural gas is for storage, opening up additional uses for current liquefied natural gas (LNG) facility upgrades already underway.

Renewable power to hydrogen, alternatively, requires less upfront capital investment due to its relatively simple process that can be incorporated into existing systems. However, those existing systems cannot accommodate 100% pure hydrogen fuel, so existing storage and transmission infrastructure will need to be upgraded eventually as technology advances enough to burn a higher percentage of hydrogen. This could result in a larger investment, long term, for power to hydrogen.

In addition to the cost disparities, utilities must also consider the carbon dioxide aspect of each fuel. Hydrogen is identified as a 100% carbon neutral fuel because it does not emit carbon dioxide when used. Methane is a net-zero carbon fuel in that it removes carbon dioxide from the atmosphere to create methane, but then burning the gas then emits the same amount of carbon dioxide back into the atmosphere. Though still a renewable fuel, not all states acknowledge this a no-carbon process yet, so methane may not fully contribute to carbon neutrality goals right now.

While technology and legislative advancements are still on the horizon, the development of power-to-renewable gas facilities are moving forward. According to an article in Power magazine, the world’s first fully integrated power-to-hydrogen-to-power project was launched in June 2020. The industrial-scale project will convert a 12-megawatt electrical (MWe) combined heat and power plant in France to hydrogen. By its estimated completion in April 2024, the project seeks to achieve full operation and production with high-hydrogen fuel mixtures of at least 80% to 100%.

Though still a new, innovative process, power conversion to methane or hydrogen gas looks to be the solution utilities need to support the increasingly lofty goals of decarbonization while addressing the intermittency of renewable energy.

 

The world’s energy portfolio is changing dramatically in response to renewable power resources. Learn how harnessing the power of renewable natural gases can enhance energy resilience and enable a decarbonization.

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Brian Elwell, PE, is a senior project manager for engineer-procure-construct (EPC) projects focusing on the development and execution of energy-related design-build solutions. His responsibilities include preliminary feasibility studies; comprehensive program analyses including financial analyses, conceptual and detailed design; and complete design-build program management from conception through implementation.